In a Universal Mobile Telecommunication System (UMTS), the process for establishing a Packet Data Protocol (PDP) context by a user equipment (UE) is as shown in FIG. 1.
Firstly, the UE sends an Activate PDP Context Request message containing parameters such as a Network Layer Service Access Point Identifier (NSAPI) and a Transaction Identifier (TI) to a Serving General Packet Radio Service Support Node (SGSN). The NSAPI is an identifier assigned by the UE to identify an established PDP context, and is used between the SGSN and a Gateway General Packet Radio Service Support Node (GGSN). The TI is a transaction identifier assigned by the UE to identify the established PDP context and is used between the UE and the SGSN. After the PDP context is established, the TI is recorded by the UE and the SGSN; during subsequent operations (for example, modification and deactivation) on the PDP context, for example, in a Modify PDP Context or Deactivate PDP Context Request message, the PDP context is associated with the TI instead of the NSAPI.
In a Long Term Evolved (LTE) network system, an Evolved Packet System (EPS) Bearer ID is corresponding to the NSAPI, but the identifier is assigned by a Mobility Management Entity (MME) instead of the UE, and in an NAS message between the UE and the MME, the bearer is identified by the EPS Bearer ID, and identifier information similar to the TI does not exist.
In addition, in an R8 network, the concept of default bearer is introduced, that is, when the UE accesses a System Architecture Evolved (SAE) network through an Evolved Universal Terrestrial Radio Access Network (EUTRAN), the UE firstly establishes the default bearer, and the default bearer cannot be deleted, if the default bearer is deleted, a dedicated bearer corresponding to the default bearer will be deleted as well; when the UE accesses the SAE through a GSM/EDGE Radio Access Network/Universal Terrestril Radio Access Network (GERAN/UTRAN), the concept similar to the default bearer is also adopted, and the UE having EUTRAN ability activates an interactive or background PDP context after being attached to the GERAN/UTRAN.
In the prior art, the UE establishes the bearer context in the EUTRAN, and the UE and the MME identify the bearer by the EPS bearer ID. After the UE moves to 2G/3G, in the subsequent operations on the PDP context, for example, updating the PDP context, for the NAS message between the UE and the SGSN, the PDP context will be identified by the TI, but TI information does not exist in the UE and the SGSN at this time, so that the process cannot normally works.